Butt Pimples?

Idk why but whenever I shave sometimes I get pimples underneath my buttcheeks but more near my vagina. But its still on my butt. And they get really annoying, ive been only shaving there once a week, and when i do i soak in the bath for awhile. Afterwards id put lotion on my butt. Its been helping and making my butt really smooth but sometimes they come back after i shave. Any suggestions on what to do to help them be more preventable?